Which of the following statements are true?① piston pumps are self-priming.② piston pumps require high maintenance.③ piston pumps have low cost of production.④ piston pumps have low volumetric efficiency.
A. ① and ②
B. ③ and ④
C. ① and ③
D. all the above
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The most common methods to solve the problem of oil trapped or surrounded oil in gear pump are as follows: ().
A. reduces the speed
B. designs with unloading groove
C. increases the oil suction port
D. reduces the gas temperature
For a gear pump, if the output pressure is less than the rated pressure and is not zero, and the speed remains unchanged, the relationships of a. actual flow, b. theoretical flow and c. rated flow should be ().
A. b>a>c
B. a>b>c
C. c>a>b
In order to make the gear of gear pump mesh smoothly, seal the suction oil chamber strictly and supply oil evenly and continuously, the overlap coefficient r of gear meshing must be made () 1.
A. greater than
B. equal to
C. less than
There are three leakage ways in CB-B gear pump and _________ has the greatest impact on volumetric efficiency. ()
A. gear end clearance
B. gear tip clearance
C. gear base clearance
D. A + B + C